jetting..... aggghh

6 replies to this topic
  • harv_wr426

Posted August 03, 2007 - 04:57 PM


i hav an 02 wr426. not had the bike long and its my first 4 stroke. bit of a step up from my tired 92 cr125 so i'm not exactly an expert on these new 4 strokes. anyway.... the bike starts from cold no problem but front of exhaust is glowing red after a couple of minutes or less at idle. is this normal or running too lean? after about 20 mins running the bike starts to splutter and wont run at low revs and runs ruff and backfires if throttle is fully open until eventually it stops and wont start again until cold no matter how many times u kick it. took plug out and it was black with soot. new plug in, same thing again. sounds like its running too rich? could the pilot be too lean and the main too rich? never heard of that case before.

its a fair bit of a question indeed but hope somone can help

  • Mutu

Posted August 04, 2007 - 12:20 AM

Have a look through and see what others are using.
Do you know what your jetting settings are?

  • gujm666

Posted August 04, 2007 - 06:43 PM


well you might want to check your jet the guy above said..the reason why its getting red hot ("red head") is because wr's arent made to idol...they dont cool quickly enough when not moving...get it moving and itll cool down...just dont let it idle and not move for like over a few minutes or its gonna get reallyyyyyyy hot...i have a wr 400f yamaha and it will do this but i dont stop riding...just turn of your bike when not riding it...:prof: :blah: :banghead:

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  • byggd

Posted August 05, 2007 - 04:48 AM


Start by removing the carb, taking it apart and cleaning it. While in there make a note of the jet sizes and needle setting. You say you are new to thumpers so this should help. Let us know what you find.

  • harv_wr426

Posted August 20, 2007 - 12:27 PM


thanks. yeah i took the carb apart and cealend it out, there was a bit of crap in the pilot jet. she seems to be running pretty well now, starts first kick hot or cold. i'v added a small in-line fuel filter to avoid any more crap getting into the carb

  • jbrooks26

Posted August 20, 2007 - 12:31 PM


Another thing to note about these carbs. You will want to make a habbit of once or twice a year at a minimum, removing the hot start and choke assemblies to clean and lubricate them. They can get sticky and hard to work, when this happens they don't seal properly and can cause very strange problems. Hope this helps, and congrats on the purchase of one of the most bulletproof bikes out there.


  • byggd

Posted August 20, 2007 - 01:48 PM


Harv, can you buy sea foam fuel treatment over there? If so get a bottle, it will help keep the carb trouble free.


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